Digging A HoleI've been thinking about a game idea for a while now.
It's a 19th century tale of a young man who inherits a fantastical drilling machine from his eccentric uncle, who invented all kinds of strange contraptions. The young man reads his uncle's diary (there's always a diary, isn't there) and discovers that his uncle was dead set on drilling through the center of the earth, only to come out on the other side.
Our hero decides to try this himself, and once he enters the earth, he finds other entire worlds inside his own, full of remarkable civilizations and creatures. In the process, the hero beings to decipher some of his uncle's strange inventions, which can aid him on his quest. The Remarkable Goggles Of Optical Penetration, for example, allow him to see special features of landscapes that only show up when wearing them.
It's very steampunk-y, which makes the inventions both elaborate and distinctive, and it obviously has a strong Jules Verne influence.